Regulation of expression of human intestinal bile acid-binding protein in Caco-2 cells.
Molecular mechanisms of the bile acid active transport system in the ileal enterocytes remain unknown. We examined whether bile acids affect human enterocyte gene expression of intestinal bile acid-binding protein (I-BABP), a component of this transport system. Differentiated Caco-2 cells were incubated in the presence of human bile, bile acids or other lipids. The level of I-BABP expression was evaluated by Northern and Western blot analyses. A 24 h incubation of Caco-2 cells in a medium containing either bile or bile acids resulted in a remarkable 7.5-fold increase in the I-BABP mRNA level over the control level. Neither cholesterol, palmitic acid, phosphatidylcholine nor cholestyramine treated bile showed any difference in I-BABP mRNA expression from the control. Bile acid treatment increased the level of I-BABP mRNA in Caco-2 cells in a time- and dose-dependent manner. Western blot analysis showed that this induction led to increase in cytosolic I-BABP. Chenodeoxycholic acid and deoxycholic acid showed greater induction effects than other hydrophilic bile acids, including their own glycine conjugates. Pretreatment by actinomycin D or cycloheximide completely inhibited the up-regulation of I-BABP expression by bile acid. Bile acids, especially lipophilic bile acids, increase the I-BABP expression in Caco-2-cells, suggesting that luminal bile acids play an important role in regulating the I-BABP gene expression.
Kanda
T
T
Department of Surgery, Niigata University School of Medicine, 1-757 Asahimachi-dori, Niigata 951, Japan.
Foucand
L
L
Nakamura
Y
Y
Niot
I
I
Besnard
P
P
Fujita
M
M
Sakai
Y
Y
Hatakeyama
K
K
Ono
T
T
Fujii
H
H
D001647:Bile Acids and Salts / Q000502:physiology*; D018938:Caco-2 Cells / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases; D007082:Ileum / Q000502:physiology*; D008562:Membrane Glycoproteins; D008875:Middle Aged; D018996:Myelin P2 Protein / Q000235:genetics; D009363:Neoplasm Proteins; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
D001647:Bile Acids and Salts; D002352:Carrier Proteins; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D006913:Hydroxysteroid Dehydrogenases; D008562:Membrane Glycoproteins; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D025521:Tumor Suppressor Proteins; C107608:FABP7 protein, human; C037643:bile acid binding proteins; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)